Circulation issues and im stumped....

3 Feb 2008
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United Kingdom
Been trying without success to coax some life into the outlaw's heating this evening. Boiler is Glow Worm 80FF, pump is Grundfos 15/50, fully pumped S plan, with Honeywell motorised valves. There is however no room stat, CH motorised valve I presume is energised from the programmer when CH is selected.

No complaints regarding shortage of HW, and cylinder is hot at top. Motorised valves seem to be ok, no resistance on the levers when energised. System is (over) full, F+E tank up to overflow, but I think this may be a faulty ballvalve, will change asap. Drained some water off from kitchen rad on ground floor, it was a bit black, but to be expected, no inhibitor in system at present. F+E could be heard refilling.

Flow from boiler rises into airing cupboard, turns horizontally into air seperator, from there down to pump, splitting below pump to MV's. Manual 15mm bypass from above MV's, partially open.

With HW off/CH on at programmer, both MV's are as expected. Yet practically no heat in rads. Pipes have got hot as far as Rads, shutting all rads down then opening 1 at a time did get each rad very hot. However then reopening all the rads, the lot went cold and no amount of coaxing could get any heat into them. There is a gate valve on flow into cylinder, also closed that to force full circulation (if any!) around CH. Pipe from CH MV is very hot to touch as far as the floor where is disappears.

Manually opening HW MV on the lever, hot water from the boiler shot through to the cylinder. Although it seems a definate circulation issue with the CH, im unsure as to if the HW is coping on a gravity circulation and the pump is goosed. Pump is making a noise, and is extremely hot to touch, but alteration of speed doesn't seem to change the noise level as I would expect. Bled pump, water present, no audible indication of cavitation.

If anyone could offer a 2nd opinion i'd be grateful. Had enough by 8.30 p.m. tonight so left it, but as things are quiet will go back tomorrow. My daughter lives there with them, she's not very well and cold so i'm keen to sort it out!

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Very common for air seps to block up and allow just enough heated water through to do hot water and one rad at a time when all others off as you have tried. sometimes block all way down to pump valve
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Thanks, I'll give it a go DIA. Any other possibles if this not the case? Cold feed connects into the air seperator, it did refill ok when I drained a couple of gallons off.

Sorry Tony and Namsag, I was writing while you posted, all options welcome!
If the valve is opening, and you can take the actuator off to check that, there can't be much else but a pot full of sludge.
The gate valve on pipe to cylinder should not be left closed.
You could try closing the by-pass valve more, that will prevent the water taking the easy route back to boiler. However it's likely the pump outlet and inlet orifaces are reduced by silt and restricting the flow. Perhaps time for new pump
Easy enough to take actuator off a Honeywell I think, will try that. It has let water by though today, ive had the kitchen rad HOT and thats the furthest on system. Air Sep has been replaced in not distant past im told.
Thanks MANDATE, I only closed the gate valve as a temporary measure to try and force any flow around the rads. It didnt solve anything so reopened it to allow the cylinder to heat if nothing else.....
Thanks again to all for their input, it is appreciated.

Arrived this morning and felt the warmth as soon as I walked in, really at a loss to explain but bloody thing fired up this morning and worked a treat. :confused:

Very happy family, and extremely happy daughter so a result!

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